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56 NOVA SCOTIAN ECHINODERMATA.—HONEYMAN. 
eries Exhibition a large number of star fishes caught in the act 
of swallowing oysters were exhibited. 
We have also Crenaster-papposus ; the “Sun Star” of the 
Family Solasteriadae and Hippasteria phrygiana, the “Cush- 
ion Star” of the Family Astropectenidae. 
The fourth order is Hchinoidea. 
Of this order we have a representative of the Family Hchin- 
idue; Echinus drobrachienses, our common sea urchin. This 
differs from the preceding in having the animal enclosed in a 
test of spherical form which bristles all over with spines of differ- 
ent sizes. When alive and in the aquarium, the spines, which 
have a “ball and socket” movement, are seen moving in all 
directions. Beyond these stretch the tentacles, which protrude 
from ten perforated zones. These, too, are in motion ready to 
catch any creature of convenient size and proper for food that 
may come within reach. This is thereby conveyed to the mouth, 
which occupies a central position below. This differs from that 
of the other echinoderms which we have already described, in 
having teeth. There are jive of these arranged as a pentagon. 
They are set in jaws of equal number, which may be seen on 
opening the test. This masticatory apparatus is known as 
“ Aristotle’s Lantern.” The anus is on the summit. When the 
spines are removed the structure of the test is then observable. 
The spines are beautifully formed. Their structure can only be 
properly seen by the microscope. They have sockets which fit 
the tubercules with which the test is ornamented. The perfor- 
ations from which the tentacles protruded are now distinctly 
seen. The test is composed of calcareous plates, which are nicely 
fitted together and firmly cemented. These plates have names 
according to their position and functions. Certain ones surround 
the mouth, the oral, and also the anus, the anal. The latter are 
surrounded by the genital plates, which are five in number and 
of pentagonal form. Each of these has a perforation. One of 
them is larger than the others. This has a spongy, minutely 
perforated tubercule, like the rose of a watering pot — the 
“madre poriform tubercule.” Wedged in between the plates and 
occupying the summits of the ambulacral areas are five smaller 
